Vibronic measuring devices are used in industrial measurements technology, especially also in connection with the control and monitoring of automated manufacturing processes, for highly accurate ascertaining of one or more measured variables, especially a mass flow rate, a density and/or a viscosity of a medium, for example, a liquid or a gas, flowing in a process line, for example, a pipeline. Vibronic measuring devices are often formed by means of a measuring device electronics (which is most often formed by means of at least one microprocessor) as well as a measuring transducer of vibration-type electrically connected with the measuring device electronics and flowed-through during operation by the medium to be measured. Such measuring devices, for example, embodied as so-called four conductor—or also so-called two conductor devices, have been known for a long time, not least of all also in the form of Coriolis mass flow, density measuring devices or also in the form of viscosity, density measuring devices, and are established in industrial use. Examples of such vibronic measuring devices, respectively suitable measuring transducers, are described in, among other things, US-A 2006/0081069, US-A 2004/0123645, US-A 2006/0096390, US-A 2007/0062309, US-A 2007/0119264, US-A 2008/0047362, US-A 2008/0190195, US-A 2008/0250871, US-A 2010/0005887, US-A 2010/0011882, US-A 2010/0257943, US-A 2011/0161017, US-A 2011/0219872, US-A 2011/0265580, US-A 2012/0123705, US-A 2013/0042700, U.S. Pat. No. 4,491,009, U.S. Pat. No. 4,524,610, U.S. Pat. No. 4,756,198, U.S. Pat. No. 4,777,833, U.S. Pat. No. 4,801,897, U.S. Pat. No. 4,876,898, U.S. Pat. No. 4,996,871, U.S. Pat. No. 5,287,754, U.S. Pat. No. 5,291,792, U.S. Pat. No. 5,349,872, U.S. Pat. No. 5,531,126, U.S. Pat. No. 5,705,754, U.S. Pat. No. 5,796,010, U.S. Pat. No. 5,796,011, U.S. Pat. No. 5,831,178, U.S. Pat. No. 5,945,609, U.S. Pat. No. 5,965,824, U.S. Pat. No. 6,006,609, U.S. Pat. No. 6,092,429, U.S. Pat. No. 6,223,605, U.S. Pat. No. 6,311,136, U.S. Pat. No. 6,477,901, U.S. Pat. No. 6,513,393, U.S. Pat. No. 6,651,513, U.S. Pat. No. 6,666,098, U.S. Pat. No. 6,711,958, U.S. Pat. No. 6,840,109, U.S. Pat. No. 6,920,798, U.S. Pat. No. 7,017,424, U.S. Pat. No. 7,077,014, U.S. Pat. No. 7,200,503, U.S. Pat. No. 7,216,549, U.S. Pat. No. 7,325,462, U.S. Pat. No. 7,360,451, U.S. Pat. No. 7,792,646, WO-A 00/34748, WO-A 01/02 816, WO-A 2007/043996, WO-A 2008/059262, WO-A 2013/092104, WO-A 85/05677, WO-A 88/02853, WO-A 89/00679, WO-A 94/21999, WO-A 95/03528, WO-A 95/16897, WO-A 95/29385, WO-A 98/02725, and WO-A 99/40 394.
Measuring transducers of the measuring devices shown therein comprise at least one at least sectionally straight and/or at least sectionally curved, e.g. U-, V-, S-, Z- or Ω shaped, measuring tube having a lumen surrounded by a tube wall for guiding the medium.
The at least one measuring tube of such measuring transducers is adapted to guide medium in the lumen and concurrently to be so caused to vibrate that it executes wanted oscillations, namely mechanical oscillations, about a resting position with a wanted frequency also co-determined by the density of the medium and consequently usable as a measure for the density. In the case of conventional vibronic measuring devices, typically, bending oscillations at a natural resonant frequency serve as wanted oscillations, for example, such bending oscillations, which correspond to a measuring transducer inherent, natural bending oscillation, fundamental mode, in which the oscillations of the measuring tube are resonant oscillations, which have exactly one oscillatory antinode. The wanted oscillations are in the case of an at least sectionally curved measuring tube additionally typically so embodied that the measuring tube moves about an imaginary oscillation axis imaginarily connecting an inlet-side and an outlet-side end of the measuring tube in a pendulum-like manner as a kind of end clamped cantilever, while, in contrast, in the case of measuring transducers with a straight measuring tube the wanted oscillations are most often bending oscillations in a single imaginary plane of oscillation. It is additionally known for the purpose of performing repeated reviews of the measuring transducer during operation of the measuring device to excite the at least one measuring tube, at times, also for temporarily lasting times, to execute oscillations outside of resonance as well as to evaluate the oscillations outside of resonance, for example, in order, such as described in US-A 2012/0123705, to detect possible damage to the at least one measuring tube as early as possible, damage which can bring about an undesired lessening of the accuracy of measurement and/or the operational safety of the respective measuring device. In the case of measuring transducers with two measuring tubes, these are most often integrated into the particular process line via a distributor piece extending on the inlet side between the measuring tubes and an inlet-side connecting flange as well as via a distributor piece extending on the outlet side between the measuring tubes and an outlet-side connecting flange. In the case of measuring transducers with a single measuring tube, the latter communicates with the process line most often via a connecting tube opening on the inlet side as well as via a connecting tube opening on the outlet side. Furthermore, measuring transducers with a single measuring tube additionally comprise at least one counteroscillator of one or a plurality of parts. The counteroscillator is embodied, for example, to be tube-, box- or plate-shaped and is coupled to the measuring tube at a first coupling zone on the inlet side and to the measuring tube at a second coupling zone on the outlet side. During operation, the counteroscillator essentially rests or oscillates oppositely to the measuring tube. The inner part of the measuring transducer formed by means of measuring tube and counteroscillator is most often held alone by means of the two connecting tubes, via which the measuring tube communicates with the process line during operation, in a protective measuring transducer housing, especially in a manner enabling oscillations of the inner part relative to the measuring transducer housing. In the case of the measuring transducers shown, for example, in U.S. Pat. No. 5,291,792, U.S. Pat. No. 5,796,010, U.S. Pat. No. 5,945,609, U.S. Pat. No. 7,077,014, US-A 2007/0119264, WO-A 01/02 816 and WO-A 99/40 394 with a single, essentially straight, measuring tube, the latter and the counteroscillator are, such as quite usual in the case of conventional measuring transducers, essentially coaxially oriented relative to one another. Thus, the counteroscillator is embodied as an essentially straight hollow cylinder and so arranged in the measuring transducer that the measuring tube is at least partially jacketed by the counteroscillator. Materials used for such counteroscillators, especially also in the case of application of titanium, tantalum or zirconium for the measuring tube, are most often comparatively cost effective steel types, such as, for instance, structural steel or free-machining steel.
For active exciting, respectively maintaining, of oscillations of the at least one measuring tube, not least of all also the wanted oscillations, measuring transducers of vibration-type have, additionally, at least one electromechanical oscillation exciter acting during operation differentially on the at least one measuring tube and the, in given cases, present counteroscillator, respectively the, in given cases, present, other measuring tube. The oscillation exciter is electrically connected with the measuring device electronics by means of a pair of electrical connecting lines, for example, in the form of connection wires and/or in the form of conductive traces of a flexible circuit board, and serves, especially, operated by an electrical exciter signal generated by the measuring device electronics and correspondingly conditioned, namely at least per se matched to changing oscillation characteristics of the at least one measuring tube, to convert an electrical excitation power fed by means of the exciter signal into a drive force acting at a point of engagement on the at least one measuring tube formed by the oscillation exciter.
Oscillation exciters of usually marketed measuring transducers of vibration-type are typically constructed as a kind of oscillation coil working according to the electrodynamic principle, namely formed by means of a coil—in the case of measuring transducers with a measuring tube and a counteroscillator coupled thereto, most often affixed to the latter—as well as, serving as armature interacting with the at least one coil, a permanent magnet, which is affixed correspondingly to the measuring tube to be moved. The permanent magnet and the coil are, in such case, usually so oriented that they extend essentially coaxially to one another. Additionally, in the case of conventional measuring transducers, the oscillation exciter is most often so embodied and placed that it acts essentially centrally on the at least one measuring tube. Alternatively to an oscillation exciter acting rather centrally and directly on the measuring tube, it is possible, such as disclosed, among others, in the above cited U.S. Pat. No. 6,092,429, for example, also to use exciter mechanisms formed by means of two oscillation exciters affixed not in the center of the measuring tube, but, instead, rather on the inlet—, respectively on the outlet side thereof for the active exciting of mechanical oscillations of the at least one measuring tube or, such as, among other things, provided in U.S. Pat. No. 6,223,605 or U.S. Pat. No. 5,531,126, for example, also formed by means of an oscillation exciter acting between the, in given cases, present counteroscillator and the measuring transducer housing.
For registering oscillatory movements of the at least one measuring tube, not least of all also those corresponding to the wanted oscillations, measuring transducer of the type being discussed have, furthermore, mounted on the measuring tube, for example, electrically connected with the measuring device electronics by means of a pair of electrical connecting lines, at least one oscillation sensor, which is adapted to convert the oscillatory movements into an oscillation measurement signal representing such and containing a signal frequency corresponding to the wanted frequency, and to provide the oscillation measurement signal to the measuring device electronics, for example, namely a measuring—and operating circuit of the measuring device electronics formed by means of at least one microprocessor, for additional processing. In the case of measuring transducers of usually marketed vibronic density measuring devices, the oscillation sensors are most often likewise of electrodynamic type, consequently constructed in the manner of a solenoid. Accordingly, also the oscillation sensors of such a sensor arrangement are most often likewise formed respectively by means of a permanent magnet affixed on the measuring tube and at least one coil—, for example, affixed to the, in given cases present, other measuring tube or to the, in given cases present, counteroscillator—and permeated by a magnetic field of the permanent magnet. As a result of the oscillatory movements of the at least one measuring tube, the coil provides, at least at times, an induced measurement voltage.
Due to the wanted oscillations of the at least one measuring tube,—not least of all also for the case, in which the wanted oscillations of the at least one measuring tube are bending oscillations—, as is known, also Coriolis forces dependent on the instantaneous mass flow rate can be induced in the flowing medium. These can, in turn, bring about Coriolis oscillations dependent on the mass flow rate. The Coriolis oscillations superimpose on the wanted oscillations and have the wanted frequency. This occurs in such a manner that between inlet-side and outlet-side oscillatory movements of the at least one measuring tube performing wanted oscillations and at the same time flowed-through by the medium, a travel time—, respectively phase difference, can be detected, which is also dependent on the mass flow rate and, consequently, also usable as a measure for mass flow measurement. In the case of an at least sectionally curved measuring tube, in the case of which selected for the wanted oscillations is an oscillation form, in which the measuring tube is caused to move like a pendulum in the form of an end clamped cantilever, the resulting Coriolis oscillations correspond, for example, to that bending oscillation mode—, at times, also referenced as a twist-mode—, in which the measuring tube executes rotary oscillations about an imaginary rotary oscillation axis directed perpendicular to the imaginary oscillation axis, while, in contrast, in the case of a straight measuring tube, whose wanted oscillations are embodied as bending oscillations in a single imaginary plane of oscillation, the Coriolis oscillations are, for example, developed as bending oscillations essentially coplanar with the wanted oscillations. For the above already mentioned case, in which by means of the measuring device supplementally to density additionally also the mass flow rate of the respective medium guided in the measuring transducer should be ascertained, measuring transducers of the type being discussed have for the purpose of registering both inlet-side as well as also outlet-side oscillatory movements of the at least one measuring tube and for producing at least two electrical oscillation measurement signals influenced by the mass flow rate to be measured, furthermore, most often spaced from one another along the measuring tube, two or more oscillation sensors, which are so embodied and arranged that the oscillation measurement signals generated therewith and led to the measuring device electronics have not only, such as already mentioned, in each case, a wanted signal component, but that additionally also between the wanted signal components of the two oscillation measurement signals a travel time, respectively phase difference, dependent on the mass flow rate is measurable. Alternatively or supplementally to measuring also the mass flow rate supplementally to measuring the density, it is—such as already mentioned, respectively, among other things, shown in the above US-A 2011/0265580—additionally also possible, by means of such measuring transducers of vibration-type, consequently by means of therewith formed vibronic density measuring devices, supplementally also directly to measure a viscosity of the through flowing medium, for example, based on an electrical excitation power required for exciting, respectively maintaining, the wanted oscillations, respectively based on a damping of the wanted oscillations ascertained based on the excitation power, and to output such in the form of qualified viscosity measured values.
A coil applied in the case of a measuring transducer of the type being discussed—, for example, to form an oscillation exciter or an oscillation sensor—typically includes a coil support, for example, one of a synthetic material, such as a plastic, and/or a ceramic and/or a metal. The coil support has a straight passageway extending from a first end of the coil support formed by a first end face to a second end of the coil support distal to the first end and formed by a second end face, especially a second end face parallel to the first end face. Wound around the coil support is a coil wire of an electrically conductive material, for example, copper or platinum, respectively an alloy thereof, for example, a coil wire coated with an electrically insulating lacquer layer. The final mounting of such a coil is typically done using a screw positioned in the passageway of the coil support to attach the coil wire carrying coil support to the counteroscillator, respectively to the measuring tube, of the respective measuring transducer. Typically thereafter, consequently in the case of coil already located in the installed position, each of the two connecting line is electrically conductively connected, for example, namely manually soldered, to respective ends of the coil wire.
Due to the often very small distances between the individual already joined together assemblies of the measuring transducer to be manufactured, not least of all in the case of measuring transducers of lesser nominal diameter, respectively having comparatively small measuring tubes, a not insignificant measure of dexterity is necessary in the case of handling the connecting lines, respectively the operating means required for soldering, brazing, such as, for instance, a corresponding hand soldering device, respectively the corresponding solder material. This is coupled with a correspondingly increased risk, first of all, of producing unrecognized, defectively soldered connections. Moreover, there is in the case of soldering, brazing the connecting lines to the coil located in the installed position an increased risk of tearing the most often very thin coil wire, respectively damaging the equally only very thin insulation of the same, consequently of damaging or even destroying the coil.